Tripod constant-velocity joint

A tripod constant-velocity joint comprising:

• an inner ring attached to a leg shaft;
• three trunnions protruding from the inner ring toward an outer peripheral side of the inner ring, each of the three trunnions having a convex outer-circumferential surface;
• three roller units rotatably supported by the respective three trunnions;
• and
• a outer ring storing the three roller units,
• wherein the inner ring is disposed in the outer ring such that the inner ring is unrotatable relative to the outer ring and is movable relative to the outer ring in a direction of an outer ring axis about which the cylindrical outer ring is to be rotated,
• wherein each of the three roller units includes:
• an inner roller slidably fitted at an inner circumferential surface thereof on the convex outer-circumferential surface of a corresponding one of the three trunnions, such that the inner circumferential surface of the inner roller and the convex outer-circumferential surface of the corresponding one of the three trunnions are in contact with each other at a tangent point that is to be reciprocatively moved during rotation of the tripod constant-velocity joint;
• a plurality of cylindrical rolling elements each including a crowned end portion in an axial end portion thereof;
• an outer roller supported by the inner roller through the plurality of cylindrical rolling elements that are interposed between the inner roller and the outer roller;
• and
• a limiting portion provided integrally in the outer roller and protruding from the outer roller toward an inner peripheral side of the outer roller, so as to limit movements of the plurality of cylindrical rolling elements and the inner roller,
• wherein the inner roller and the limiting portion cooperate to define therebetween a clearance in a direction of a center line of a corresponding one of the three trunnions, such that the clearance is smaller than an axial length of the crowned end portion of each of the plurality of cylindrical rolling elements, and is larger than a stroke distance of reciprocating movement of the tangent point when a joint angle of the tripod constant-velocity joint is a predetermined value,
• wherein the joint angle of the tripod constant-velocity joint is defined as an angle between the outer ring axis and an inner ring axis about which the inner ring is to be rotated, and
• wherein the clearance is larger than the stroke distance of reciprocating movement of the tangent point when the joint angle is 6 degrees.